Which schedule delivers reinforcement for the first response after a fixed duration has elapsed since the last reinforcement?

• A. Fixed Interval
• B. Fixed Ratio
• C. Extraneous Variable
• D. Functional Relation

Answer: (A)

Reinforcement schedules include the fixed interval schedule, where reinforcement is delivered for the first response after a fixed amount of time has passed since the last reinforcement. After a reinforcement occurs, the clock starts again; any responses made before that fixed duration ends aren’t reinforced, and as the interval nears its end the organism tends to respond more quickly, producing a post-reinforcement pause followed by a rise in response rate as the time for the next reinforcement approaches. This distinguishes it from fixed ratio, which depends on a set number of responses rather than time; and from variable interval, which uses an unpredictable duration. Extraneous variable and functional relation aren’t schedules themselves—they refer to concepts outside this time-based reinforcement pattern.